P.J.C. Signore

Low temperature magnetic measurements of NENP

The temperature dependent magnetic susceptibility, χ(T), of two samples of the S=1 linear-chain Heisenberg antiferromagnet Ni(C2H8N2)2NO2(ClO4), known as NENP, has been measured from 400 K to 264 µK. Our measurements are in agreement with existing results of other researchers who worked above 1.2 K. Below 1.2 K, χ(T) increases with decreasing temperature. The results suggest that this increase is intrinsic to the NENP and is not a consequence of a single source of paramagnetic impurities in the samples.

S=1 Heisenberg chain Ni(C2H8N2)2Ni(CN)4 in the frame of strong coupling theory

Our previous experimental study has identified Ni(C2H8N2)2Ni(CN)4 (NENC) as an S=1 antiferromagnetic (AF) Heisenberg chain with strong planar anisotropy D/kB≈6 K and D/|J|≈7.5. The position of the system in the (D,λ) phase diagram ((7.5,1) in units J) has enabled the study of excitons as elementary excitations from the singlet ground state (SGS). Strong coupling theory for the thermodynamics of 1d S=1 large—D systems is used for the re—analysis of specific heat and susceptibility data. The influence of in—plane anisotropy and exciton interactions is discussed.

Low temperature magnetic investigations of NINAZ

Abstract The temperature dependent magnetic susceptibility of the S=1 linear-chain Heisenberg antiferromagnet Ni(C 3 H 10 N 2 ) 2 N 3 (ClO 4 ), known as NINAZ, has been studied from 60 mK to 300 K. Below 1.5 K, a large increase in the susceptibility has been observed in poly-crystalline and powdered samples. Similar to earlier work on NENP, our results are interpreted in terms of the presence of end-chain spins.

Experimental evidence of excitons in Ni(en)2Ni(CN)4

Abstract Specific heat and susceptibility measurements were performed on Ni(C 2 H 8 N 2 ) 2 Ni(CN) 4 between nominally 50 mK and 20 K. The results indicate the material is an S = 1 Heisenberg chain system with D / k = 6 K and D /| J | = 10–20. The low-temperature specific heat results suggest, for the first time, the presence of magnetic excitations known as (anti) excitons.

Low-temperature magnetic susceptibility and resistivity measurements and electron probe microanalysis of Y1−xUxPd3

Abstract We have extended the low-temperature magnetic susceptibility and resistivity measurements of Y1−xUxPd3 (x ≈ 0.2) down to millikelvin temperatures. One sample showed Curie-Weiss-like paramagnetic susceptibility between 50 mK and 2 K. Another small sample appeared to have nearly constant susceptibility between 400 μK and 120 mK. The signal arising from paramagnetic impurities has been estimated from the susceptibility of undoped YPd3 measured between 600 μK and 170 mK. No signature of superconductivity was observed in the resistivity measurements down to 5 mK. Electron probe microanalysis showed that the sample composition was modulated on a scale of tens of micrometers.

Ultralow temperature inductive measurements of YbBiPt

Abstract Low frequency magnetic susceptibility measurements have been performed on YbBiPt from 3 to 800 mK. In addition to the known peak at 400 mK, an anomaly exists near 120 mK. The lowest temperature feature arises from a surface phase (e.g. Bi 2 Pt) and is not a property of the main material. No additional features in the susceptibility are attributed to the bulk material down to the lowest temperature.